New Asparagus Taking No Rot

Researchers near Lincoln have gone back to nature in a ground-breaking project to grow disease-resistant asparagus.

The Aspara Pacific team, led by plant breeder Peter Falloon, has produced several hybrid asparagus that resist the root disease Phytophthora without the aid of chemicals.

“These asparagus have yields and quality as good as or better than the best available commercial varieties,” Dr Falloon says.

The team began by identifying a source of resistance to the disease. “We had to start from scratch because no one else in the world had ever found genetic resistance to Phytophthora in asparagus,” Dr Falloon says.

Traditional methods – “no genetic engineering” – were used to breed the new asparagus.

In a process called “recurrent selection”, the researchers exposed seedlings to Phytophthora and selected the surviving plants. Seeds from these plants were grown for another generation, exposed again, and so on, to slowly improve the disease resistance. Having improved the resistance, the researchers then worked on producing varieties that also had good yield and spear quality.

Aspara Pacific is working with the Asparagus Council to evaluate the resulting hybrids.

Phytophthora is a serious problem worldwide. It cuts yields by up to 50 percent and can cause fields to be pulled out earlier than the usual productive period of 15 years. Re-establishing the crop is costly for growers.

The Aspara Pacific project – funded by the Foundation for Research, Science and Technology and the Asparagus Council – is expected to reduce growers’ reliance on Metalaxyl, the main chemical used to fight Phytophthora.

“Metalaxyl has been used repeatedly over the years,” Dr Falloon says. “However, it’s becoming ineffective. Some micro-organisms in the soil actually eat it and are thriving on it, leaving less available to fight the Phytophthora, so the grower has to increase the dosage.”

Asparagus is New Zealand’s third-most valuable horticultural export, after onions and squash. In 1999, about 1300 tonnes valued at nearly $6 million was sent in cans to Australia and Japan imported about 1200 tonnes of fresh asparagus valued at more than $11 million.

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